Pumps play an important role in a variety of medical procedures. For example, pumps have been used to deliver fluids (saline, etc.) to treatment areas during laparoscopic and endoscopic procedures, to transport blood to and from dialysis and heart-lung machines, and to sample bodily fluids for analysis. Most medical pumps are centrifugal or positive displacement pumps positioned outside the surgical field and designed to withdraw or deliver fluid.
Positive displacement pumps generally fall into two categories, single rotor and multiple rotors. The rotors can be vanes, buckets, rollers, slippers, pistons, gears, and/or teeth which draw or force fluids through a fluid chamber. Conventional rotors are driven by electrical or combustion motors that directly or indirectly drive the rotors. For example, peristaltic pumps generally include a flexible tube fitted inside a circular pump casing and a rotating mechanism with a number of rollers (rotors). As the rotating mechanism turns, the rollers compress a portion of the tube and force fluid through an inner passageway within the tube. Peristaltic pumps are typically used to pump clean or sterile fluids because the pumping mechanism (rotating mechanism and rollers) does not directly contact the fluid, thereby reducing the chance of cross contamination.
Other conventional positive displacement pumps, such as gear or lobe pumps, use rotating elements that force fluid through a fluid chamber. For example, lobe pumps include two or more rotors having a series of lobes positioned thereon. A motor rotates the rotor, causing the lobes to mesh together and drive fluid through the fluid chamber.
Centrifugal pumps include radial, mixed, and axial flow pumps. Centrifugal pumps can include a rotating impeller with radially positioned vanes. Fluid enters the pump and is drawn into a space between the vanes. The rotating action of the impeller then forces the fluid outward via centrifugal force generated by the rotating action of the impeller.
While effective, current pumps require large housings to encase the mechanical pumping mechanism, gears, and motors, thereby limiting their usefulness in some medical procedures. Accordingly, there is a need for improved methods and devices for delivering fluids.